The algorithm of noisy k-means

In this note, we introduce a new algorithm to deal with finite dimensional clustering with errors in variables. The design of this algorithm is based on recent theoretical advances (see Loustau (2013a,b)) in statistical learning with errors in variables. As the previous mentioned papers, the algorithm mixes different tools from the inverse problem literature and the machine learning community. Coarsely, it is based on a two-step procedure: (1) a deconvolution step to deal with noisy inputs and (2) Newton's iterations as the popular k-means

The Tolerability of Risk

peer reviewe

La perception sociale des risques: étude de cas sur les champs électromagnétiques en Belgique

Dans le cadre de cette étude, nous avons voulu mesurer la perception sociale du risque relatif à l’exposition aux champs électromagnétiques. Notre objectif était d’identifier les modes de connaissances auxquels se référent des individus qui font face à un risque empreint d’un niveau élevé d’incertitude scientifique. Comment ce public, mobilisé autour d’une problématique complexe, acquiert-il un niveau d’expertise suffisant pour comprendre les enjeux multiples (sociaux, économiques, éthiques, politiques et environnementaux) d’une technologie sur la société et ses modes d’organisation ? Quelle vision a-t-il des acteurs politiques et subpolitiques (Beck, 2001) qui prennent part aux débats ? Quel niveau de confiance accorde-t-il à un monde politique qui, en cas de risque majeur, pourrait invoquer une démarche précautionneuse et récupérer une partie du pouvoir décisionnel qui semblait lui échapper (Brunet, Delvenne & Joris, 2007) ? En situation de haute incertitude scientifique, qui sont les experts ? Quelle relation entretiennent les différents stakeholders 1 avec les autorités publiques? Le risque électromagnétique constitue un exemple éclairant de nouveau risque technologique, qui suscite une mobilisation sociale particulière et met en évidence les défis technologiques, sociaux, éthiques et politiques que nos sociétés occidentales doivent affronter à l’aube du XXIe siècle

Angular analysis of the rare decay Λb→Λ(1520)(→NK)ℓ+ℓ−\Lambda_b\to \Lambda(1520)(\to NK)\ell^+\ell^-

We study the differential decay rate for the rare decay $\Lambda_b\to \Lambda(1520)(\to NK)\ell^+\ell^-$ where $\ell$ is a light lepton, as this decay mode can provide new and complementary constraints on the Wilson coefficients in $b\to s\ell^+\ell^-$ transitions compared to other modes. We provide a determination of the complete angular distribution, assuming unpolarised $\Lambda_b$ baryons and neglecting the lepton mass. The resulting angular observables are expressed in terms of helicity amplitudes involving hadronic form factors within the Standard Model and New physics models with chirality-flipped operators. We study these observables at low and large $\Lambda$ recoils, using effective theories to determine relations among the hadronic form factors involved. As there is currently no determination of the form factors available from lattice simulations or light-cone sum rules, we perform a first illustration of the sensitivity of some observables to New Physics contributions using hadronic inputs from quark models.Comment: 37 pages, 5 figures. Corrected typos in Section 2 and Appendix A. Numerical Illustrations updated from arXiv:1108.6129v2 to arXiv:1108.6129v

Novel differentially private mechanisms for graphs

In this paper, we introduce new methods for releasing differentially private graphs. Our techniques are based on a new way to distribute noise among edges weights. More precisely, we rely on the addition of noise whose amplitude is edge-calibrated and optimize the distribution of the privacy budget among subsets of edges. The generic privacy framework that we propose can capture all privacy notions introduced so far in the literature to release graphs in a differentially private manner. Furthermore, experimental results on real datasets show that our methods outperform the standard existing techniques, in particular in terms of the preservation of utility. In addition, these experiments show that our mechanisms guarantee epsilon-differential privacy for a reasonable level of privacy epsilon, while preserving the spectral information of the input graph

O princípio da precaução como uma ferramenta estratégica para redesenhar a (sub)política. Compreensão e perspectivas da ciência política de língua francesa.

O princípio da precaução está inserido em um contexto decisional em evolução, marcado por uma incerteza multidimensional com relação às conseqüências ambientais, econômicas, sociais, éticas e políticas das inovações tecnológicas. Na ciência política de língua francesa, o princípio funciona como uma ferramenta estratégica, uma resposta política ao surgimento de um novo fluxo de incerteza social, voltada principalmente para as inseguranças do mundo científico. Neste trabalho, afirmamos que o princípio da precaução redefine a forma de gerir a incerteza científica, em uma sociedade caracterizada pela indefinição das fronteiras entre atores políticos e subpolíticos. Em sua aplicação, há uma linha de ruptura que reduz a margem de manobra decisória de determinadas entidades subpolíticas, enquanto incentiva outras a agirem. Contudo, enfatizamos que, em um mundo cada vez mais globalizado e interligado, os efeitos da aplicação do princípio da precaução são temporários e locais. Ainda assim, o princípio pode contribuir para os importantes debates a serem desenvolvidos em espaços institucionais, para uma ação reflexiva antecipatória e de apoio à decisão

Characterization and mobility of arsenic and heavy metalsinsoils polluted by the destruction of arsenic-containingshells from the Great War

International audienceDestruction of chemical munitions from World War I has caused extensive local top soil contamination by arsenic and heavy metals. The biogeochemical behavior of toxic elements is poorly documented in this type of environment. Four soils were sampled presenting different levels of contamination. The range of As concentrations in the samples was 1937–72,820 mg/kg. Concentrations of Zn, Cu and Pb reached 90,190 mg/kg, 9113 mg/kg and 5777 mg/kg, respectively. The high clay content of the subsoil and large amounts of charcoal from the use of firewood during the burning process constitute an ample reservoir of metals and As-binding materials. However, SEM–EDS observations showed different forms of association for metals and As. In metal-rich grains, several phases were identified: crystalline phases, where arsenate secondary minerals were detected, and an amorphous phase rich in Fe, Zn, Cu, and As. The secondary arsenate minerals, identified by XRD, were adamite and olivenite (zinc and copper arsenates, respectively) and two pharmacosiderites. The amorphous material was the principal carrier of As and metals in the central part of the site. This singular mineral assemblage probably resulted from the heat treatment of arsenic-containing shells. Microbial characterization included total cell counts, respiration, and determination of As(III)-oxidizing activities. Results showed the presence of microorganisms actively contributing to metabolism of carbon and arsenic, even in the most polluted soil, thereby influencing the fate of bioavailable As on the site. However, the mobility of As correlated mainly with the availability of iron sinks